The teenage actor beat out Ben Mendelsohn and Jason Segel.

The Beasts of No Nation actor, who is 15 years old, beat out fellow actors Ben Mendelsohn (Mississippi Grind ), Christopher Abbott (James White), Jason Segel (The End of the Tour ) and Koudous Seihon (Mediterranea) for the honor.

The smiling first-time performer thanked everyone from his fellow winner and co-star Idris Elba to the Netflix film's director, Cary Fukunaga, to the costume designers when he took the stage.

Earlier in the night, Elba brought the young actor from Ghana up with him to share his best supporting male actor award. "I couldn't have done it without you," Elba told Attah.

Attah played child soldier Agu in the African war drama, which was Netflix's first original narrative film.

During the show's opening monologue, co-hosts Kumail Nanjiani andKate McKinnon joked about the roundup of this year's films while mentioning Beast of No Nation, Room and Spotlight. "This year's nominees cover a wide variety of difficult subjects ranging from child abuse to even worse child abuse," said Nanjiani. Jacob Tremblay, 9, of Room, was also in attendance as a presenter.

Jessica Chastain presented the award to Attah during the ceremony, which was held at the Santa Monica Pier and aired on IFC.

Attah wasn't the only first-time performer to take home an award: Mya Taylor made history as the first transgender winner when the actress won best supporting female for Tangerine.